Control means



F. A. MITCHELL CONTROL MEANS Nov: 30, 1937.

Filed March 13, 1934 4 Sheets-Sheet l Nov. 30, 1937. A. MITCHELL CONTROL MEANS File` March l5, 1934 4 Sheets-Sheet 2 INVENTOR FRANK ALLEN MVTCHELL BY W62 ATTORNEY F. A. MITCHELL CONTROL MEANS Nov. 30, 1937.

Filed March l5,

4 Sheets-Sheet 5 a m oc/ooooooo Nov. 30, 1937. F- A. MlTCHELL 2,100,609

CONTROL MEANS Filed March 13, 1954 4 Sheets-Sheet 4 Cil Patented Nov. 3o, 1937 UNITED STATES 2,l.i)t,609

CONTRGL MEANS Frank Allenl Mitchell, London, England, assignor to Electric and Musical Industries Limited,

Hayes, Middlesex, Great Britain Application March i3,

England, a company of i934, Serial No. 715,266

In Great Britain March le, i933 9 Claims.

The present invention relates to means for controlling and indicating the setting of apparatus for modulated carrier wave reception such, for example, as wireless receivers and provides new or improved means whereby the setting of the apparatus may be controlled and indicated either at the apparatus or from a position remote from the apparatus.

In connection with the steering of ships and for other purposes it has been proposed to make use of a drum having a, conducting surface divided into two relatively insulated parts along helical' lines. A number of fixed contacts are arranged in contact with the drum surface and the drum is mechanically coupled to an electric motor and a driven member such as the rudder of a ship. The arrangement is such that when the circuit of one of the xed contacts is closed at a remote point, provided that this contact is resting 'against a conducting part of the drum surface, the motor will start to rotate and will be stopped automatically when the contact reaches the insulating `zone separating the conducting zones on the drum surface. The motor has been arranged to rotate in one direction when contact is made with one of the two conducting surfaces of the drum-and inthe opposite direction when contact is made with the other conducting surface. Such an arrangement is not suitable for use in connection with the tuning ot' wireless receivers because it is capable of adjustment to only a certain number of iiXed positions deterfmined by the positions of the contacts which have hitherto been arranged along a line parallel to the drumaxis. For tuning a wireless receiver to any one of a number of stations it is necessary that the various tuning positions which can be selected should be adjustable with considerable exactitude. f'

According to the present invention, therefore, there are provided means for eilecting the ad-a justment of a tuning component voi a wireless receiver, said means comprising a driving mem- 'ber having said component anda movable elec trical contact breaking device both mechanically coupled thereto, the Contact breaking device beingadapted, during Contact between the greater part of a surface thereof anda contacting cierne1 ber, to cause or permit motion of the driving member and, during contact between said contactingy member and a zone of said surface, to prevent or interrupt said motion, said Zone run= ning in a direction or in directions inclined at an acute angle with respect to the direction or rco-a tion thereof, characterised in that coutact= ing member is so mounted as to be adjustable in position for the purpose of varying the position of the contact breaking device at which contact is made between said contacting member and said insulating zone.

According to a feature of the present invention it is arranged thatappreciable movement oi the contact breaking device can take place whilst the contacting member is in contact with the insulating zone and means are provided whereby the contact breaking device can be caused to take up a position substantially at one edge ci the insulating zone.

Other features of the present invention will appear from the following description and the appended claims.

The invention is illustrated by way of example in the accompanying drawings in whicii- Fig. l is a diagram showing the circuit con nections between the various components of remote control apparatus according to the present invention,

Fig. 2 is a view in elevation showing mecha,

nism .for automatically tuning a radio set using the circuit arrangements of Fig. i,

Fig. 3 is a plan view of a manual control switch shown in Fig. 2 which may be provided upon the wireless receiver itself to enable the way in which the receiver can be used to be adjusted,

Figs. il and 5 are end views ci details shown in Fig. 2,

liig. 6 shows a detail which appears diagrama matically in Fig. l,

Fig. 'l is a plan view of a station selector, of the kind shown in Fig. i, in the :toria ci a oi Europe,

Fig. S shows a connecting device whereby the station selector oi Fig. 7 can be connected to the automatic tiuzingjinechanism of Fig. 2,

Fig. 9 is an underside View of the map shown in Fig. 7,

Eg. lo is a section et Fig. 9 on the line .ir-c2,

Fig. ll shows a selector plug which may used with the map of l'ig. il or 'the panel ci Fig. l2,

Fig. l2 is a plan view of an alternative stasrl tion selector in the fome ci a plain panel,

Fig. i3 is a plan view of form ci dial which may "ce used with the 'manual control switch shown in v`Fig. 3,

Figs. le and l5 are detail views illustrating operation oi iine tuning,

Figs. i6 and i7 show in plan and elevation re-= spectively an alternative arrangement to that 9i e. and

Fig. 18 shows a simplified form of mechanism for automatic station finding according to this invention.

j Like parts in the various gures are given the same references and for making clearer the relationship between the various figures, points on `diierent pieces of apparatus which are electrically connected together and the wire connecting these points arein many cases given the same numeral reference with a diiferent alphabetical suix.

Referring now to Figs. 1 to 11 and, in the first place, more particularly Fig. 2, beneath the panel H@ of a combined wireless receiver and talking machine is mounted a four gang variable condenser |32 which is adapted in known manner to tune the various circuits of the receiver to a desired wavelength. The condenser shaft 8| carries a toothed wheel 'i8 meshing with a pinion upon the shaft of a knob |03 whereby the receiver can be tuned manually. The setting of the condenser can be read upon a translucent scale lthrough window H2. The scale is illuminated by means of an electric bulb 56A with the aid of a mirror H3. Geared to the shaft of the control knob |03, and hence to the condenser shaft 8|, is an electrical motor l0 of the induction ldisc type comprising an induction disc 14 carried upon the motor shaft 15. This mot-or is of known type and has a current coil 'll and two potential coils 'l2 and 13.

Above the motor there is xed to the motor shaft l5 a disc '56. A second disc Hd is rotatably mounted on the shaft '|5 and is pressed into frictional engagement with the discs lli by means of a spring H5. As will be seen from Fig. 4 the disc I Hl carries two pins H6. When the motor is rotating the friction between the discs 1B and H4 is sucient to cause one of the pins H6 (ac cording to the` direction of rotation) to close the two switches l |'i and H8 but the switches automatically open when the motor is no longer energized. The purpose of the switches Hl and H8 will be described later.

T o the lower en d' of the condenser shaft 8| is xed a drum ||9 acting as the movable member of a contact breaking selector device which is also shown in underside plan or end view in Fig. 5. T he drum is of insulating material and has two conducting surfaces 83 and 841- thereon. These surfaces are separated from one another along two zones 82 and |20, the zone 82 being inclined at an acute angle to the direction of motion of the drum surface, in this case it is of approximately helical shape. The Zone |20 may be helical or parallel to the drum axis. The zone 82 is arranged to extend around about one quarterI of the periphery of the drum.

Two sets of contacts are provided, one set being designated by the references |C to ISC and f the other set by references MC to 26C. Only4 )certain .of these references, for example 6C, are for clearness marked on the drawings. The same numerals with diierent sumxes are used on the drawings to designate points electrically connected with the respective contacts. Each contact is carried by a spring blade such as |D anchored to an insulating support |22 by suitable screws |23 (see Fig. 5).A The position of each contact around the drum axis can be adjusted within limits by means of adjusting screws of which f our only are indicated in Figs. 2 and 5 at 3A, 4A, |3A and MA. The screws are, as shown in Fig. 5, staggered to facilitate their adjustment. Suitable lock nuts may be provided for securing the adjusting screws in position after they have been set as required.

To the lower end of the shaft el is xed a cam disc BS co-operating with switch contact blades lllW and HW (seen better in Fig. 1). A pin |05 projecting from the cam disc B5 co-operates with switch contact blades NW1 and 53W. In Fig. 1 the mechanism is represented diagrammatically as a simple cam. The arrangement is such that contacts MS and HS remain closed excepting at one extreme position of the variable condenser |2 and that contacts llSi and 53S remain open excepting at the opposite extreme position of the condenser.

On the panel HB is a button 99 serving to operate a switch and a control knob 93 operating switch mechanism also shown in Fig. 3, the view of Fig. 3 being a plan view with the knob 93 and panel IIB removed. The functions of these switches will be described later with reference to Fig. 1 Where they are shown diagrammatically.

Turning now to Figs. '7 to 11, there is shown in Fig. 'l a plan view of one form of selector panel 5B which can be used with the apparatus above described. This panel can, if desired, be mounted upon the cabinet of the radio receiver or as shown it can be located at a remote point and connected to the receiver by means of a multi-core flexible cable BT. For this purpose there is shown in Fig. 8 a multi-pin plug member 38 which can be plugged into a corresponding socket member 89 xed vat any convenient place upon the radio receiver. The numerals appearing against the various contact Aplugs and sockets indicate the points in the apparatus to which the sufx E. It will be .noticed that certainl of the holes are designated with a numeral having the suffix B. Such holes correspond to long wave transmit-ting stations, and in a manner to be described later, can in some cases make use of the same drum contact as a particular medium Wave station. numeral, for example iE and 1B, are therefore connected together.

The sockets indicated by the same.

On the selector panel is a pilot lamp 56, a-

volume control knob 5l, a press button 59 and two additional sockets marked Oi and Gram respectively, the functions of which will be described later. The numerals against these additional sockets also indicate the vpoints to which they are connected.

Fig. 9 is an underside view of the selector panel of Fig. 7 with the base removed and Fig. 10 lis a sectional view along the line :zz-x of Fig. 9. The selector panel comprises an upper metal plate 53 which bears the representation of the map. This may for example be embossed. Beneath the plate 53 is fixed an insulating plate 56 having eyelets marked 1E, 1B, etc., as already described according to the selector contacts to which they are connected. The bottom of the panel is constituted by a metal plate 52 which, however, may be covered externally by insulating means since in operation itis at mains poten- 75 alcance This member 5| is mounted upon four balls 55 arranged in suitable recesses in the underside of the member 5| and resting upon the basey plate The member 5| is also restrained by pivot arms |2i so as to be capable only of lateral movement. It is held in one direction by a spring |24 and in this end position the switch constituted by contacts 34S and 36S is closed. The connecting point to the upper metal plate 53 is indicated by SilF and that-to the base plate 52 by reference 3lF. The switch contacts actuated by button 59 are indicated by 2S, iS and 36S, respectively. A rheostat 58 is controlled by the knob 5l and acts as a loudspeaker volume control. Its terminals are indicated by 32E and 33E.

As will be seen in Figs. l and ll, there is provided a selector plug 6U having an outer insulating casing 63 having fixed within it a central pin 62. Over this pin is arranged a sleeve til which is slidable thereon. The sleeve urged into its lowermost position by a spring Gil. The lower part or" the sleeve 6| is split longitudinally to make it yielding. When the selector plug d@ is inserted into one of the holes of the panel, forexample hole B as in Fig. l0, the sleeve @i first makesifeontact betweenv the upper plate 53 and the'socktli. On further insertion it engages the sidei v-a-countersunk hole in the insulating plate because this hole is not-exactly aligned .with the hole 4B, and forces the plate 5l to the v leitthus opening vswitch 34S-, 3dS. This as will appeal later has the effect of changing the condition of the receiver from that adapted for inedium wave reception to that ior long wave reception. The Ssleeve 6| cannot new be pushed further because oi" a shoulder thereon engaging the upper plate E53 and consequently iurther pressure upon the plug casing 53 causes the central pin E2 to move downward, against the action oi .the spring 64, and make contact the base plate 52. When pressure upon the plug casing 63 ceases, the pin- 62 recedes and breaks contact with the plate 52. The same action will take place when the plug is inserted` into any hole marked with the suiix B, that isa hole corresponding to a long wave station. The holes corresponding to short wave stations and bearing the suix E are however aligned with the holes in the platel5| and when the plug is inserted into one of these the switch contacts 36S, 36S remain closed. i

The most important electrical connections will be seen in the circuit diagram of Fig. l. Here the wires or like conductors connecting two points are given the same numeral reference Ias the points connected together with the suflix W.

The mains terminals MG and 3l are connected to a suitable alternating current source and se long as contacts 40S, MS remain closed (that is excepting at one extreme position oi the variable tuning condenser) the primary oi the transformer i225 is energized. The terminals 42T of one secondary winding are connected tothe radio receiver to provide the necessary power for operation. The other secondary winding has its ter-v minals 3H, 33T connected to the-pilot lamps 5b (uponv the selector panel) and 56A (upon the receiver panel). These -lamps indicate when the set is in operation.

ferently in Fig. 1 for the sake of clearness. For

example only one bank of contacts l@ to |3C are shown and the operation of the 'apparatus is described for clearness as if only vthis set were provided. Further the two switch devices with contact arms 94 and 95 shown in Fig. i are actually superimposed and operated by the single knob 93. in Fig. 2. The switch arm 94 serves to make Contact between the ring 44 and one or other of the studs 30S, MS, etc. The switch arm 95 makes contact with one end on the brokenring EEP and with its other end on segment 34P.

The circuit arrangement will be best understood by a description of certain examples of its mode of operation. The knob 93 (Fig. 2) will be assumed to be so set that arms 94 and 95 in Fig. l are in the positions shown. In Fig. 13 is shown a dial which may be associated with the knob Q3 and with the setting above mentioned the word Remote may appear in the dial window in the selector panel as shown in Fig. l. They rst eniect of inserting the plug is to connect top plate 53 (shown beneath the member 54 in Fig. l) with the socket 4B. Further it will cause `the plate 5l to move sideways and open contacts 35S and as shown. Finally contact will be made between socket @E and base plate 52. It will be noted that the motor coil terminals MM, l lll/i1 and MM2 are permanently connected to the mains terminal il G. The other mains terminal is permanently connected to base plate 52 by wire till/V. After the plug has been inserted and whilst it is pressed into contact with base plate 52, a circuit can be traced from the base plate 52 (at mains potential) on the one hand through plate 5ft by wire SlbW, switch contact to contact ring (lli and thence to terminal 35M oi the current coil li, thus energizing the current coil. On the other hand a circuit can be traced from vplate 52 through socket 3B, by wire 5W, drum contactdc, conducting drum surface tt, contact l0 through wire HW to the terminal lll/i of potential coil l2, thus also completing the circuit through the potential coil l2. It is arranged that for all working positions of the drum ila, the contact 53C remains in contact with surface 84 and contact l@ remains in conn tact with 'surface-r The effect of energizing coils ll and 'l of the motoris to make the motor start up and run in such a direction that the upper surface of the drum M9 moves to the right in Fig. l.. The effect yof energizing coils 'il and it on the other hand is in the opposite direction.`

For the moment it will be assumed that pressure on the selector plug tu is maintained. The drum will rotate until vcontact 2C comes to rest upon the insulating zone 82 when the circuit of coil` l2 is interrupted. Current will still iow through the' coil 'li but nevertheless the motor will stop. If the drum should overshoot so that contact #C came to rest upon the drum surface 84, the circuit of coil i3 would be closed and the `drum would move back untilfthe contact came to rest upon they insulating zone 82.

Now the contact C has previously been so ad justed that when the drum I9 is in such a positicn that the contact 4C rests on'the insulating zone 82, the condenser tunes the receiver approximately to the wavelength of; Paris.

to make the drum move.

It is, however, undesirable that pressure should have to be maintained upon the selector plug S0 whilst the station is being/selected. On the other hand it is also undesirable that the current coil 'li should remain energized whilst the set is in operation, as would be the case were the selector plug designed to make permanent connection with the plate 52 when inserted. To overcome both these diiculties there is provided the friction clutch device 16, Il already described in connection with Fig. 2. In Fig. l the essential part of this clutch device is depicted diagrammatically, 'l5 representing the motor shaft and .16 the disc frictionally coupled thereto. For the sake of clearness the two switches operated by the friction disc 'I5 are shown upon opposite sides thereof. When the motor commences to rotate, owing to momentary contact between the central pin of the selector plug and the base plate 52, the friction disc 'l5 is carried around until both the switches SIS, MS and 55S, 55S are closed and then slips upon the shaft l5. remain closed so long as the motor coils are energized but automatically open, owing to the spring blades of these contacts, when the coils cease to be energized. The eect of the closure of contacts SIS, 45S is to override the contact between the selector plug t@ and the plate 52 and to maintain connection between plates 52 and 53. Thus it is only necessary to press the selector plug 65 down momentarily so that the coils II and 'I2 are energized and the motor commences to move. energized by switch SiS, 66S. The switches 3IS, 56S and 55S, 56S are closed irrespective of the direction of the motor. Thus if when the selector plug was inserted lthe contact 5C had been resting on surface 56 the motor would have run in the opposite direction but the switches would still be closed. When the contact QB comes to rest upon the insulating zone 52, the circuit of the coil 'I2 is interrupted, the motor comes to rest and switch SIS, MIS opens thereby interrupting the circuit of coil il.

The switch 66S, 15S serves to mute the receiver (that is to render it inoperative and silent) during the operation of tuning. This may be done by connecting contact 35S to a suitable point on vthe receiver which is then earthed, through 55S, (ISP, switch arm 55 and wire 35W, whilst the motor is rotating and open circuited again when the motor comes to rest (and when ythe receiver is therefore tuned to the. desired station). The receiver can be muted in any convenient manner, for example by short-circuiting the H. F. or L. F. amplifiers or loudspeaker.

It has been found highly desirable to arrange ample clearance between the contacts 3C etc. and the edges of the conduct/ing drum surfaces 83 and 8d when the contacts are resting upon the insulating zone 52. The preferred form of the contacts and the groove constituting the insulating zone can best be seen from the enlarged view of Fig. 14. Unless this ample clearance is provided arcing is likely to take place and to upset completely the operation of the device. It is not possible, however, to provide such ample clearance and at the same time to ensure that stations are suihciently accurately tuned in wherever the contact may come to rest in the groove unless a relatively large drum be used. In practice it has not been found convenient to provide drums of suicient size to satisfy these requirements. There is accordingly provided, upon the selector panel, a ne tuning button 55.

These contacts Thereafter the coils are kept attracco the insulating zone, the button 59 is pressed.

The eiect of this is to join wires IW and 30W to wire 3IW and therefore to the mains terminal SIG thus energizing coils 1I and 'I2 and causing the motor to move the top of the drum II9 to the right in Fig. 1. 'As soon as the contact 5C makes contact with the edge of surface 84, as shown in Fig. l5, the coil 'I3 is also energized owing to terminal ESM being connected to mains terminal SIG through contact ISC, drum surface 86, contact 5C, wire QW, socket QB, plate 53, switch blades SUS and IS1 and plate' 52. Thus the current coil li and both potential coils I2 and I3 are energized, the motor has an` equal tendency to rotate in opposite directions and it consequently comes to rest with the contact 5C resting just against the edge of surface 84. Since the correct tuning position is obtained when the contact rests against the edge of the groove, the desired station can be accurately tuned in.

The rheostat 58 with its control 5l serve to control the volume of sound emitted by the loudspeaker of the receiver. In the example ,illustrated volume control is effected by arranging the resistance 58 inparallel with the moving coil IQII of the loudspeaker which itself is not illustra-ted. As shown in Fig. 9 terminals IUI may cepting that the member 5I is not displaced and consequently the switch 35S, 36S is closed. The eifect of this is to connect a suitable source of current 200 connected to terminals 35, 36, across a relay Il which is shown in more detail in Fig. 6. 'I'he relay contacts il are thus closed and in this position short circuit a part of a high frequency tuning coil 20| in the receiver. This coil is then tuned by the variable condenser IGZ to a medium wave station. Clearly 'any desired number of contacts el can be operated by the relay Il so that any desired number of coils in the receiver can be controlled simultaneously. It is because of this action ofthe switch 35S, 36S that it is possible to arrange that one Wire such as IW for example, serves to control the selection of both a long and a short wave station.

When the selector plug 60 is plugged into hole 2E, marked Gram on the selector panel, contact 2C is energized and the drum H9 rotates until this contact comes into the groove 52. In this extreme drum position the switch cam 86 closes contactslISi, 53S, (keeping contacts 50S, IES closed also) and thus energizes the talking machine motor (not shown) which is connected to terminals 63M. The switch M51, 53S, or other switches operated similarly by the cam can be arranged also to connect the pick-up device, instead of the high frequency amplier, to the low frequency amplifier of the receiver. It can also be arranged that the button 59 on the selector panel, under these circumstances, serves when pressed to initiate a change of record, if the talking machine is of a suitable magazine type. `When the selector plug 60 is plugged into hole IEE, marked Off, contact I2C is energized and the drum IIS rotates into its other extreme position. In this position both switches MS, ISIS and liSl, 63S are open. 'I'he opening of the l former switch serves tion by manipulating knob more than l to out oi the mains from the receiver. f

The purpose of the switch device controlled by knob 93 on the receiver-Vis not only to permit the apparatus to be set, at will, either for remote operation or for operation at the receiver but also to permitl automatic selection of certain stations from the receiver itself. When the switch arm 94 is turned. away from stud 30S, the selector panel is disconnected from the receiver. If the arm 94 be moved to stud 4S the same eiect is produced as by inserting the selector plug 60 into the hole 4E in the selector panel in the previous example. In all settings such that the selector arm 95 is out of contact with segment 34P, the stations selected are long Wave stations. When contact is made with segment 34E' the relay |04 is operated and the stations selected are medium wave stations. When the arms B4 and 95 are so set that arm 94 is on stud |01S, the receiver can be tunedA manually to any desired long wave sta- |03 in the usual way. When the stud |08S is engaged by arm 94 the receiver can be tuned manually to a desired medium wave station because in this position arm 95 is in contact with segment 34P. By turning the switch on to stud The fact that the relay |04 is energized in this position is not material if the supply of current connected to terminals 35, v36 is derived from the mains transformer |2S.

It will be noted that whenhand tuning the muting switch S, 46S is not operative to mute the receiver because arm 05 is then out of contact with ring 4BP. If desired, however, the muting switch may be made operative when hand tuning so long as the tuning knob is being -.rotated by any considerable amount. It can be arranged that small movements of the knob |03 can be carried out, however, for line tuning without operating the muting switch.

The button S9 provided upon the receiver panel i lill serves the same purpose as button on the selector panel, as will be seen from Fig. l. l

In the arrangement oi" Fig. 1 onlyone baule of contacts HCI-l2@ is shown tio-operating with. the drum H9. With such an arrangement in order to utilize the full tuning frange of the condenser 02, namely 180, the groove 82 must run rather more than half way around the periphery of the drum. Where' it is desired to select from a rela tively large number oi stations it may not be con= tenient to arrange all the necessary contacts in one row and a plurality or" rows can then be proc1 vided. In Fig. 2, two such rows are4 shown and thegroove 82 should then extend around rather a quarter oi' the periphery of the drum.

In Fig. l2 is shown an alternative :Term which the remote control panel may take. Here the holes 4E, 3B etcfin the panel in columns with the appropriate station names marked against them. The selector panel may of course take a great variety of other forms.

Figs. 16 and 17 illustrate a form of muting switch alternative to that shown in Fig. 4i. The two members 16A and 16B are fixed to the condenser shaft 8|. A contact member 36S is rotat-n ably mounted on the shaft 8| and is held in iric=- tional engagement with the member 'ISA by means of a spring H5. A contact member l5 of approximately U-shape is provided and when the condenser shaft is rotated, the member 36S makes contact with one or other limb of the member Il. thereby earthlng the latter member.

|2S the receiver is switched off.I

A are arranged.

A simplified embodiment of the present invention is shown in Figure 18. In this example no provisionis made at the remote-point lor switching the receiver on and oil, for changing the wavelength range orl ior switching the receiver over to the talking machine condition.

The connections are as shown in the drawings, terminals 3 IG and MG being connected to a suitable A. C. source. A belt or cord drive 19 is shown between the motor lo and the condenser shaft 8| carryingthe drum H9. The selector plug is in this case asimple wander plug and is connected by a short length oi flexible cable to wire 44W. The effect of inserting the plug 60 into any desired hole, for example HE, is to conneot wire 44W through contact llC and either contact |3C or lC, according to the position of the drum, to motor terminal ISM or IM. Since motor terminals tlMi and MM are connected to mains terminal MG and since wire 44W is connected through contacts MS and 3|S to mains terminal 3| G, the current coil 'Il and one half of 'the potential coil l2, 'I3 are energized. The drum is consequently rotated until the contact ITC reaches the insulating zone 82. For ne tuning 'there is provided a knob 59A whereby wire 44W can be connected through switch contactv 44S either through contact |35 to motor terminal ISM or through contact lS to motor terminal EM. The drum is thus rotated in one direction or the other so that iine tuning can be carried out. When the plug is inserted in hole tt, the switch contact MS is moved out of contact *with contact tls and the set can be tuned by hand in the usual wat.

fl great many variations can be made in the embodiments of the invention above described without departing from the scope of the invention Las defined the appended claims.. For example the commute-.tor drum llt may be replaced by a disc comprising two conducting portions` separated by an insulating Zone. The motor need not necessarily be of the induction disc type. lin some cases it need not loe reversible although it is preferably so. .li the motor is not reversibley only one insulating Zone is provided on the commutator and the commutator 'always rotates in the saine sense. lt comes to rest when the appropriate contact comes to on the :insulating zone..

The present invention can of course loe applied to the reception ci television and other signals whether these loe. mltted by radio or in the `torni oi modulated ca r oscillations along a line.

vl claim:

l. A tuning control means comprising a rotor shaft, a `frame provided insulation members. a drum secured to said rotor .shaft and mounted in said frame, said drum having a conducting surface divided into two insulated parte by insulating zones, one ci said Lcones being a spiral,

`a plurality ci contacting members adapted to sel @Sill separating said members with the spirals lying at acute angles with reference to the direction of motion of said drum, a plurality of contact members resiliently engaging said drum and screw means engagingthe rear of said contact members to ex them transversely of said drum and ladjust each of said contact members independently. I

3, 'I'he combination defined in the preceding claimin which each of said insulation zones extends through an angle of at least 90 about the axis of said drum.

4. In combination a radiorreceiver including a high frequency amplifier, means for tuning said amplifier to a desired signal frequency, an electric motor having a drive shaft, a friction clutch including a at' disc secured to said shaft and connected to said tuning means, means for enerf gizing said motor, a circuit connected to short circuit said ampliiier and including a switch, a

second disc loosely mounted on said shaft adjacent said flat disc, a spring pressing said second disc into engagement with said at kdisc and a member projecting from said second disc and arranged to close said switch when said motor shaft is rotated by said energizing means.

5. In combination, a radio receiver comprising a tunable circuit including a coil and a variable rotary condenser, an electric motor connected-to said condenser, a circuit for energizing said motor including a switch located at a point remote from said receiver and means located at said remote point connected to short circuit a portion of said coil said means being operatively connected with said switch.

6. In combination a radio receiver comprising a tunable circuit including a coil and a variable rotary condenser, an electric motor, a circuit for energizing said motor including a plate having a plurality of apertures therein, a second plate mounted adjacent said iirst plate, a plug adapted to pass through said apertures and move said seclond plate, switch means operable in response to movement of said second plate and a circuit connected to short circuit a portion of said coil under control of said switch means.v I

7. In combination a rotary tuning control device, an induction motor connected to said device and having a current coil and two potential coils, a circuit connected to energize said cury rent coil and one only of said potential coils to thereby cause rotation of said motor and a switching means mechanically connected to said tuning control device arranged to energize the other of said potential coils additionally to said current coil and said one potential` coil and thereby cause operation of said motor to cease and a cam connected to said control device and arranged to open said circuit in response to movement of said control device to its extreme position.

8. In combination, a radioreceiver comprising a tunable circuit including a coil and a variable rotary condenser, an. electric motor connected to said condenser, -a circuit for energizing said motor including a first switch, said switch comprising two separated metallic plates one of said plates having apertures therein, a plug of good conducting material adapted to be tted into said apertures and to connect said plates, a second switch located near said plug, a member mounted between said plates and arranged to be moved switch arranged to cause a portion of said coil to be short circuited.

9. In combination, a radio receiver comprising. a tunable circuit including a coil and a variable rotary condenser, an electric motor, a circuit for energizing saidA motor including a plate having.

second plate and a circuit connected to short circuit a portion of said coil under control of said switch means. y

A ALLEN MI'IC.

25 sidewise by movement of said plug to operate said second switch, and a circuit including said second 

